Ali Hamza Ahmad al-Bahlul, a 37-year-old Yemeni, told the war crimes tribunal he would boycott the hearings because he was not allowed to defend himself and did not recognise its authority.
Bahlul, an al-Qaeda propaganda specialist, appeared in court four years to the day after al-Qaeda and Taliban prisoners started arriving at the controversial US detention camp in Cuba.
Among the other Guantanamo Bay prisoners is David Hicks, the Australian born Muslim convert captured with the Taliban in the immediate aftermath of the September 11 attacks.
Mr Hicks, from Adelaide, is facing trial on charges of conspiracy to commit war crimes, attempted murder by an unprivileged belligerent and aiding the enemy.
Refused representation
The Yemeni, who is accused of conspiracy to commit terrorism, was one of the first to be moved to the camp which has been the subject of regular allegations of abuse.
Bahlul has refused to be represented by any American lawyer and even to speak to his appointed US military defender, Major Thomas Fleener, who said he is sympathetic to the Yemeni's demand to defend himself.
Bahlul acknowledged at a previous hearing in August 2004 that he was a bin Laden follower.
At the latest hearing, Bahlul announced in Arabic that he was "boycotting" the proceedings and set out his opposition to the US military court, stating that the United States an enemy of Muslims.
He referred to Abu Musab al-Zarqawi, the al-Qaeda chief in Iraq, and demanded that all Guantanamo detainees be designated prisoners of war, rather than "enemy combatants" which gives them fewer legal rights.
"We are prisoners of war and legal combatants based on our religion and our religious beliefs," he said. "We do not care about anything you call us."
Bahlul complained about the treatment of detainees and ended his speech with one word in English: "Boycott". He then placed his hands over his face to signify that he would speak no more.
Separate hearing
A separate panel will to start hearing the case of Omar Khadr, a Canadian who was 15 when he was detained in Afghanistan in 2002 and accused of killing a US military medic with a hand grenade during a battle.
The latest hearings came on the fourth anniversary of the opening of the camp for detainees rounded up in Afghanistan, Iraq and other hotspots in the "war on terror" declared by President George W Bush after the September 11, 2001 attacks on New York and Washington.
The inmates were at first kept in Camp X-Ray, which was little more than a series of cages with metal roofs.
About 500 detainees from almost 30 countries are now in Camp Delta, a newer and more modern facility. But the camp remains controversial, because the vast majority have been held without charge for nearly four years.
US authorities say they have been forced to set up special detention facilities and trials because of the special nature of the "war on terror".
But Amnesty International released fresh claims of torture and ill treatment of suspects.